This invention relates to novel photographic processes, elements and physical developer solutions. In a particular aspect, it relates to novel tellurium (II) complexes that are stabilized by coordination to various sulfur containing ligands which catalytically decompose in the presence of metal nuclei.
In the photographic field, many different imaging processes are known, ranging from silver halide processes to various "non-conventional" processes such as diazo processes, photopolymerization and various direct printout or photochromic processes. High speed photographic processes are especially useful and are generally characterized by an amplification step. In such processes, a catalyst is generally formed by the exposure of a photosensitive compound and the image or latent image thus formed is then used to catalyze the reduction of a material in a high oxidation state to a visible image in a low oxidation state. In silver halide processes for example, exposure of silver halide to light results in the formation of silver nuclei which then catalyze the further reduction of silver halide to silver in the presence of a reducing agent.
It is known in the art to produce tellurium images by the disproportionation of tellurium dihalides. In U.S. Pat. No. 3,700,448 to Hillson et al, a process wherein a tellurium dihalide undergoes disproportionation to form a tellurium image in the presence of catalytic nuclei and a processing liquid is described. Some unexposed tellurium dihalides of Hillson et al however, are dark in color so that image discrimination is poor. Further, tellurium dihalides are unstable in air and undergo light induced decomposition only when moistened with an organic solvent.
It is also known that certain telliurm (IV) compounds, wherein the tellurium is bonded directly to a carbon atom, undergo reduction to tellurium (O) when incorporated in a matrix with a photoreductant. In British Pat. No. 1,405,628, published September 10, 1975, there is described a process wherein tellurium (IV) ##STR1## undergoes unit quantum photoreduction to yield a tellurium (O) image. Because this process is not catalytic, i.e. the tellurium (O) does not catalyze the decomposition of the tellurium (IV) compound, this process is inherently slow thereby limiting its usefulness.